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WATERMELON FIELD DAY
* AGRICULTURAL RESEARCH CENTER, LEERUB......
S<-- UNIVERSITY OF FLORIDA, IFtAS I ,E i VRY
June 4, 1975 [ -UlE LIBRARY
JUN 1 7 1975
Jackson Haddox, Lake County Extension Direct r, Moderator
Welcoming Comments J. M. Crall, Director, EA r -t rlOf Floridaj
Research Center, Leesburg -
Discussions of Current Research
W. C. Adlerz, Entomologist
Rindworm control on watermelon
Watermelon mosaic survey and epidemiology
Pickleworm control on cantaloupe
D. L. Hopkins, Associate Plant Pathologist
Watermelon disease control with fungicides
Control of wilt on 'old' land
Bacterial rind necrosis of watermelon
G. W. Elmstrom, Associate Horticulturist and Chairman of
Watermelon Field Day
Watermelon and cantaloupe variety evaluation
Chemical weed control in watermelon
Current fertilizer studies at Leesburg
R. K. Showalter, Horticulturist
Review of watermelon marketing problems including
maturity standards, buyer preferences, and retailing
J. M. Crall, Plant Pathologist
Watermelon breeding topics including 'better' wilt
resistance in Jubilee, short internodes, and small
Biological control of watermelon fusarium wilt
Refreshments (Courtesy of Foremost Fertilizer Company)
Tour of Research Plots, Laurence Sistrunk, Assistant County
Leesburg ARC Research Report WG75-1
1. Rindworm Control Experimental Insecticides (Adlerz)
Purpose: Evaluation of chemicals not presently labelled for use
on watermelon to control rindworms. Standards: Dipel alone, Lannate.
Date of Planting: 5 February
Procedure: Treatments (yellow field stakes) were applied weekly
beginning 1 May, soon after first fruit set. They were applied
in 100 gal. of water at about 150 psi using 9 hollow cone nozzles
on a 14-foot boom.
Bay NTN 6E
Bay NTN 6E
San 1971 4.28E
San 1971 4.28E
Fundal SP + Dipel
Fundal SP + Dipel
0.125 lbs. each
0.125 + 0.25 lbs.
Results: 1974. Rindworm populations on mature melons were 98%
granulate cutworms. Cabbage loopers, tobacco budworms, and
granulate cutworms were all present in the plots from the time
plants were bunching size. Parasites and diseases kept rindworm
populations at low levels until melons were nearly mature. Nine
species of parasites were reared. The protozoan Microsporidium
sp. caused a significant infection and mortality in granulate
cutworms and cabbage loopers.
When cutworms developed large enough populations to require
control there was time for only 1 application of insecticide
before 1st harvest. The worm population averaged 1.8 per melon
and there were up to 12 per melon in some plots.
Insecticides most effective after only 1 application were Orthene
at 2 lbs AI/acre, Phosvel at 1 Ib AI/acre, Lannate at 0.5 and 1.0
lbs AI/acre and Monitor at 2 Ibs AI/acre.
Materials effective after additional applications were Orthene at
1 Ib AI/acre, Thuricide HPC plus Lannate 1 quart + 0.5 Ib AI/acre
and Thuricide 3 quarts.
1975. Results not available for program. Plots will be observed
on the field tour.
2. Rindworm Control Sampling Methods for Rindworms (Adlerz)
Purpose: An attempt was made to establish different levels of
worm infestation at harvest by varying the dosage and frequency
of application of 2 insecticides known to control rindworms.
We tried to determine if worm populations on rinds could be
predicted from worms on leaves.
Date.of Planting: 5 February
Procedure: Treatments (white field stakes) were applied according
to the schedules outlined below. They were applied in 100 gal. of
water at about 150 psi using 9 hollow cone nozzles on a 14-foot boom.
Melons picked 5/20, 5/28
Results: Results not available for program. Plots will be
observed on the field tour.
3. Watermelon Mosaic (Adlerz)
Purpose: A study of factors affecting development of mosaic
disease in the field and methods for its control.
Date of Planting: These observations are made on commercial
acreage and on experimental plots designed for other purposes,
so dates of planting are not uniform.
Results: Initial spread of WMV-2 is not correlated with the
activity of any one species of aphid. Many species are capable
of transmitting the virus.
In most years at Leesburg first symptoms appear after peak aphid
flights. Mosaic development takes place during periods of
declining aphid populations and may not be extensive.
Usually mosaic development is extensive whenever winged aphid
populations are large, but the effect on the crop is severe only
when peak flights are in April. When peak aphid flights are in
i-. mosaic infection is usually too late to affect the crop.
The most severe outbreaks develop when winds are sustained across
primary inoculum toward uninfected plants.
The spiraea aphid develops on a wide variety of weed, ornamental,
and crop plants and at Leesburg, often comprises most of the winged
uphid population at the time of peak aphid occurrence. Numbers
large enough to cause severe outbreak usually develop on citrus.
In 1973 aphid populations were large, peaked in April, and mosaic
wras severe. In 1974 aphid populations were large in March, too
early to affect watermelon. In 1974 and 1975 initial infection
occurred too late for a serious mosaic problem to develop. Aphids
trapped are compared in the following table.
Table 1. Aphids/trap/week on sticky boards at the laboratory farm.
March April May
1 2 3 4 1 2 3 4 1 2
1973 155 51 203 467 180 59
1974 357 37 546 87 17 91 42 26 54 13
1975 23 38 23 17 12 13 17 7 21 1
4. Pickleworm Control on Cantaloupe (Adierz)
Purpose: To compare insecticides for control of pickleworm.
Date of Planting: 3 March
Varieties: Gulfcoast and Morgan
Procedure: Treatments (white field stakes) were applied weekly
beginning 2 May at about the time of fruit set. They were
applied in 100 gal. of water at about 150 psi using 9 hollow
cone nozzles on a 14-foot boom.
Asgrow Honeydew vs. Tamdew
Results: 1974. A test similar to this was conducted in the fall
of 1974. Gulfcoast and Morgan melons were planted and sprayed as
described above. A heavy infestation of melonworms, a foliar
feeder, developed. Most effective controls were Lannate, Thiodan,
1975. Results not available for program. Plots will be observed
on the field tour.
5. Fungicide Trial (Hopkins)
Purpose: To compare fungicides for control of fungus foliar
diseases of watermelon.
Date of Planting: February 20, 1975.
Procedure: Treatments (green stakes) were applied weekly beginning
May 9. They were applied as 100 gallons of dilute spray per acre,
using a boom-sprayer.
Rate of product per acre
Benlate + Manzate 200
Difolatan-Dithane M-45 (alternating)
Difolatan + Dithane M-45
Dithane M-45 + Triton B-1956
Dithane M-45 + NuFilm 17
My choice each week
R-28921 + Manzate 200
R-28921 + Manzate 200
0.5 lb. + 1.5 lb.
2.5 pt. 1.5 lb.
1.25 pt. + 0.75 lb.
1.5 lb. + 4 oz.
1.5 lb. + 1 pt.
0.5 lb. + 1.5 lb.
0.75 lb. + 1.5 lb.
Results: 1974. Downy mildew was present but easily controlled
by all fungicide treatments. Gummy stem blight was moderate
in 1974 but increased in severity with the early June rains.
Treatments containing Difolatan and the Benlate + Manzate 200
treatment were most effective on gummy stem blight. Bravo 6F,
Dithane M-45, and Manzate 200 were also very effective.
1975. Downy mildew has rapidly moved into the test area and
become quite severe. Results of the test were not available
for the program. We will observe the plots on the field tour.
Recommended Sprays Rate (amt./acre) tn harvestI
Maneb 80% 1 1/2 2 lbs. 5
Dithane M-45 80% 1 1/2 2 Ibs. 5
Manzate 200 80% 1 1/2 2 Ibs. 5
Bravo 75% or 6F 1 1/2 2 1/2 Ibs. or NTL
1 1/2 2 1/2 pts.
Difolatan 4F 2 1/2 pts. NTL
Benlate 50% 1/4 1/2 lb. NTL
1 This is the minimum number of days allowed between the last
foliar application and harvest. NTL = no time limit.
2 Benlate does not control downy mildew or alternaria leaf
6. Control of Fusarium wilt on "old" land. (Hopkins & Elmstrom)
Purpose: To determine the effect of Smite 15G and Vorlex on
Fusarium wilt of watermelon on "old" land.
Date of Planting: March 3, 1975.
Varieties: Garrisonian (wilt susceptible) and Calhoun Gray
Procedure: The 6-ft. and broadcast Smite treatments were incor-
porated with a rotovator, and the 6-ft. and broadcast Vorlex treat-
ments were applied with a fumigant applicator. Beds were formed
immediately after the application of these treatments. The 30-in.
and 10-in. treatments of Smite and Vorlex were made after the beds
were formed. After all treatments were applied the bed surface
was sealed with approximately 0.5 inch of overhead irrigation.
The broadcast rates per acre were 200 lbs. (30 Ibs. a.i.) of
Smite 15G and 30 gal. of Vorlex.
% loss to wilt at thinning
Treatment Garrisonian Calhoun Gray
Vorlex 10-in. band 74 21
Smite 15G 10-in. band 43 4
Vorlex 30-in. band 23 2
Smite 15G 30-in. band 16 2
Vorlex 6-ft. band 35 7
Smite 15G 6-ft. band 22 1
Vorlex broadcast 28 16
Si.ite 15G broadcast 8 1
H.T h oHT, No Phosphorus, No Ammonia 86 10
Untreated 71 23
Results: 1974. Under severe wilt conditions only Smite and Vorlex
rare effective. The Smite and Vorlex were applied to 6-ft. and
3-f-. bands respectively, and the highly susceptible Garrisonian
plants wilted late in the season when the roots apparently grew
out of the treated area. The yield of Charleston Gray in the
6-ft. Smite treatments was quite acceptable, however.
1975. Early results in the table above show that some of the
Smite and Vorlex treatments are providing excellent control of
seedling wilt. Results of this test are not complete.
7. Watermelon Variety Trial (Elmstrom)
Purpose: To compare promising breeding lines and new varieties
with standard commercial varieties.
Procedure: Two-row plots in randomized blocks with 4 replications
were planted February 13.
Klondike Blue Ribbon
0-1. Fla 75-2
0-2. N.C. 74-H13
0-3. Ia 7208
0-4. Fla 75-3
Results: See Watermelon cultivars for Florida, Mimeo Report WG74-1
and Severity of bacterial rind necrosis in watermelon cultivars in
Florida, Florida State Horticultural Society Proceedings 87:184-187
The incidence of fusarium wilt in 1974 was extremely high and wilt
resistance was reflected in total yield. Ia 7208, 'Louisiana
Queen', 'Allsweet', registered 'Jubilee', and 'Smokylee' all
produced over 24 tons per acre of marketable fruit. Soluble solids
content of mature fruit was highest in 'Smokylee', 'Crimson Sweet',
and 'Klondike Blue Ribbon'.
8. Watermelon Variety/Wilt Trial (Elmstrom & Hopkins)
Purpose: To compare relative wilt resistance of various water-
Procedure: Single-row plots were planted February 21 in a field
thoroughly infested with fusarium wilt. Watermelons were grown
in this area each year for the past five seasons.
Klondike Blue Ribbon
Chilean Black Seeded
New Hampshire Midget
9. Cantaloupe Variety Trial (Elmstrom)
Purpose: To compare promising breeding lines and
with standard commercial varieties.
Procedure: Single-row plots in randomized blocks
cations were planted March 5.
with 4 repli-
PSR HD 11974
Results: See Cantaloupe Cultivars for Florida, Mimeo Report
WG73-2 and Florida State Horticultural Society Proceedings
Generally, 'Planters Jumbo', 'Gulfcoast', and 'Edisto 47' rank
higher than other cultivars in foliar disease resistance and total
yield. However for consistent high quality flesh and early yield
Saticoy and Samson have been outstanding.
10, Watermelon Herbicide Trial (Elmstrom)
Purpose: To evaluate various materials for pre-emergence control
of weeds in watermelon plots.
Procedure: Smokylee watermelon seed was planted February 24. The
following treatments were either pre-plant incorporated (ppi) or
surface applied prior to crop or weed emergence (pre):
Number Treatment lb a.i./acre Application
1 Devrinol 2 pre
2 Devrinol 2 ppi
3 Devrinol 4 pre
4 Devrinol 4 ppl
5 Devrinol 8 pre
6 Devrinol 8 ppi
7 Amex 820 1.5 ppi
8 Amex 820 3.0 ppi
9 Amex 820 4.5 ppi
10 Lasso 2 pre
11 Lasso 4 pre
12 Lasso 6 pre
13 Alanap 3 pre
14 Alanap 6 pre
15 Alanap 9 pre
16 Devrinol + Amex 820 2 + 1.5 ppi
17 Devrinol + Lasso 2 + 2 ppi
18 Devrinol + Alanap 2 + 3 ppi
19 Devrinol* 2 ppi
20 Dacthol + Chloro IPC 6.5 + 1 pre
21 Dacthol + Chloro IPC 6.5 + 2 pre
22 Na Azide 120 ppi
23 Hoed check
24 Unhoed check
A layby application over the row of Devrinol at 2 Ib a.i./acre
Results: Devrinol and Amex 820 have given/results during the past
3 years. Especially promising is the Devrinol + Amex 820 combi-
nation. See, Evaluation of herbicides for watermelon in Florida,
Florida State Horticultural Society Proceedings 87:180-184 (1974).
11. Slow-Release Fertilizer Trial (Elmstrom)
Purpose: To determine the effect of slow-release nitrogen ferti-
lizer on yield and quality of 'Charleston Gray' watermelon.
Procedure: Two-row plots with 4 replications were planted
February 21. The following treatments were applied.
Treatment Number of Total N
number applications per acre N Source
1 2 40 NH4N03, NaNo3
2 2 80 NH4N03, NaNo3
3 2 120 NH4N03, NaNo3
4 2 160 NH4N03, NaNo3
5 2 200 NH4NO3, NaNo3
6 1 120 NH4NO3, NaNo3
Uramite 40 + 'HI4,LI03 NaNo3
Uramite 40 + NH NO3, NaNo3
Uramite 80 + NH4N03, NaNo3
Uramite 80 + NH4IHO, NaNo3
Results: Sulfur-coated urea gave good results. Total N applied
could be reduced by about one-third and only one application was
necessary. Urea formaldehyde provided vigorous early growth but
ran out too early. This is the reason for supplementing the
Uramite treatments this year at layby.
12. Fertilizer Trial (Elmstrom & Hopkins)
Purpose. To determine the effect of N and K rate and ratio on
watermelon shape and on the incidence of bacterial rind necrosis.
Procedure: 'Smokylee' and 'Klondike Blue Ribbon' watermelon seed
was planted February 21. The following fertilizer treatments were
applied in split applications of ammonium nitrate and sulfate of
Results: Application of minor
applications of calcium and/or
incidence of rind necrosis.
elements as FTE 503 and foliar
boron have not reduced the
13. Cantaloupe Breeding (Elmstrom)
A limited program to develop parental lines with genetic properties
suitable for Fl hybrid seed production is continuing. An Fl line
was entered as an observational line in the Southern Cooperative
Cantaloupe Variety Trial in 1973 and 1974 and ranked first among
the observational lines. This line was entered as a replicated
entry in the 1975 trial. Incorporation into two Florida lines
of the monoecious flowering habit, which would facilitate Fl seed.
production, is nearing completion.
14. Watermelon Quality Factors (Showalter)
Watermelons have been among the most important vegetables grown in
Florida with annual values of 22 to 24 million dollars in recent
years. However, per capital consumption has declined steadily (19%
since 1950), and the watermelon industry is interested in what can
be done to improve handling, marketing and consumer demand.
Significant increases in yield of high-quality melons have resulted
from grower use of research aimed at better production methods.
However, during harvesting and marketing, watermelons are still
handled individually and without the protection of a container.
Mechanized handling and packaging techniques have been developed
for many fruits and vegetables, but any resistance to watermelon
breakage must come from the melon itself. Watermelons may be
classified as having good or poor shipping qualities on the basis
of rind thickness or toughness. 'Charleston Gray', the predominant
shipping variety, has a thinner rind than the round 'Cannonball'
and thus a higher proportion of edible flesh. The rinds of
'Charleston Gray' melons are somewhat flexible and resistant to
cracking, but internal bruising of the flesh from rough handling
is one of the most serious problems in maintaining quality after
Rinds on the blossom ends of 'Charleston Gray' and 'Congo' melons
are much thinner than on the sides and stem end, therefore, greater
care should be exercised in handling to avoid pressure or impacts
in the thin rind area. When watermelons are dropped as little as
8 inches, severe internal damage results, even in immature melons
or those with thick rinds, and yet there may be no external
evidence of damage. Many internally bruised melons reach the
consumer, and disappointment from their purchase usually leads to
buying fewer watermelons. Cartons with 2 to 5 melons and pallet
bins with 1,000 pound capacity have been evaluated to some extent
for Florida shipments, but extra costs have limited their use.
Handling problems and grade standards were principal discussion
topics at the recent annual convention of the National Watermelon
Growers and Distributors Association in Orlando, March 3-5. A
marketing research and development committee headed by John D.
Stiles, Florida Department of Agriculture and Consumer Services,
surveyed watermelon receivers this year to determine some of the
watermelon characteristics they preferred to buy. The response
18 24 pounds 50%
25 30 pounds 31%
Over 30 pounds- 15%
Preferred rind color
Gray 35% Light green 15%
Strip 23% Dark green 12%
Preferred seed color
Dark 77% No difference 23%
The 'Charleston Gray' is noted for its gray rind and dark red flesh
with high sugar content. For any variety to have good eating
quality, the flesh must be firm, crisp, juicy and sweet. These
quality factors are not found in immature or over-mature melons.
Watermelons harvested when the flesh is pale red will develop a
good red color after harvest, but total sugars do not increase
after removal from the vine. It is very difficult for a shopper
to judge the maturity and internal quality of an uncut watermelon,
cn( retailers have found increased sales by displaying cut sections
s that the eating quality is more apparent. Stores indicate that
75, of watermelon sales are cut rather than whole melons. Seed
color is a varietal characteristic and dark-colored seeds are not
an indication of eating quality as has been reported in some
produce buying guides.
Growers and shippers in Florida and other southern states have
discontinued grading melons according to the U. S. Standards before
shipment and are now concerned about receivers using the maturity
requirements of the Grade Standards to reject poor-quality melons.
The grade requirements for mature melons are based on subjective
estimates of sweetness and color. The Growers and Distributors
Association would like to base maturity on percent soluble solids.
However, sufficient information must first be obtained on existing
levels at various locations.
15. Watermelon Breeding (Crall)
A major change in the watermelon breeding program here was initiated
in 1961 when the first crosses were made to combine the high-type
resistance to fusarium wilt found in Texas W-5, Summit, Calhoun Gray,
Louisiana Queen, and perhaps some other varieties, with anthracnose
(Race 1) resistance and other characters desirable in a high quality
shipping-type watermelon. Smokylee, which was released in 1971, was
developed from this program. It was selected from a Texas W5 x
Charleston Gray cross. Other lines in advanced generations from
similar crosses are being evaluated for potential release. Most
promising are a Watson-type (long light-green melons) and several
round melon types, with various rind colors and patterns, that are
similar to Smokylee in wilt and anthracnose resistances and fruit
quality. More recently, an intense red flesh color from certain
Peacock lines was incorporated into a number of lines of various
fruit types. Most promising of them are round Watson and round
Garrison-stripe lines with black seeds, -deep red crisp-textured
flesh, tough rind texture, and excellent eating qualities. One
of them is entered in this year's.Regional Watermelon Trial, and
is being tested by several growers. Evaluation of these large-
fruited lines still constitutes a major effort in our breeding
Another important facet of our breeding program, however, was begun
in 1969, when crosses were made between several of our better large-
fruited lines and a number of small-fruited varieties, including
New Hampshire Midget, Sugar Baby, *and small-fruited varieties from
several foreign countries, especially Japan. The aim of this part
of the breeding program is to develop small-fruited varieties with
combined resistance to fusarium wilt and anthracnose, deep red
flesh, small black seeds, and other desirable fruit qualities. We
are seeking to develop varieties that might be adapted to shipping
in cartons, mostly round shapes, in a range of sizes from 4 to 20
pounds. This season these lines are mostly in the F5 or F6 gener-
ation and none is sufficiently fixed yet to warrant outside testing.
Greenhouse and field tests in 1971-72 confirmed the suspicion that
commercial seed stocks of Jubilee no longer had the same degree of
resistance to fusarium wilt as that found in original 'breeder`
seed of Jubilee. Increases of seed from "breeder' stocks were made
available to commercial seedsmen for 1972 plantings, so that
registered' (one generation removed from 'foundation") seed of
JuUblee was available in good supply from various commercial seed
sources for the 1973 season. Growers generally were willing to pay
a premium price for such seed because of its greater wilt resistance,
but seed demand far outstripped the limited supply of "registered"
or equivalent seed. Two additional procedures have been initiated
to help alleviate this situation. A selling program for further
selection in Jubilee to better fix wilt resistance at a satis-
factory level has been initiated. A backcrossing program to incor-
porate the high-type wilt resistance of Smokylee and Calhoun Gray
in Jubilee and several other varieties has been started, also.
This is a comprehensive program that requires both selfing and
backcrossing, as well as greenhouse testing, in each of 7 or 8
generations, but it is perhaps the most promising method for
accomplishing the aim of getting improved wilt resistance in
Jubilee and other commercial varieties.
In 1973 the first crosses were made between some of our better
lines and several short-internode lines from Kentucky. These
lines are in the first segregating generation in this year's
field and are undergoing preliminary evaluations.
16. Biological Control of Fusarium Wilt (Crall)
Work was started last season to evaluate several methods of
control of fusarium wilt of watermelon by use of biological
agents. This work is being continued this season but results are
still too preliminary for discussion at this time.